Database: Unique Constraints

Unique constraints in a database ensure that values in a column (or a group of columns) are unique across the table. This means that no two rows can have the same values in the specified column(s). Let's dive into the details of unique constraints in databases.

Code Snippets:

Here's an example of how to create a unique constraint in SQL:

CREATE TABLE students ( student_id INT PRIMARY KEY, student_name VARCHAR(50) UNIQUE );

Sample Examples:

Let's say we have a table 'employees' with a unique constraint on the 'employee_id' column:

CREATE TABLE employees ( employee_id INT PRIMARY KEY, employee_name VARCHAR(50), UNIQUE (employee_id) );

Now, if we try to insert a duplicate 'employee_id', we will get an error.

Common Use Cases:

• Preventing duplicate entries in a database table
• Ensuring data integrity by enforcing uniqueness

Importance in Interviews:

Understanding unique constraints is crucial for database design and normalization. Employers often ask about unique constraints in interviews to assess a candidate's knowledge of database management.

Conclusion:

Unique constraints play a vital role in maintaining data integrity and preventing duplicate entries in a database. By enforcing uniqueness, you can ensure the accuracy and reliability of your data.